Siglent SDS800X HD 12 bit DSO's

[tautech]

Bringing a question by PM from member @hip here for all to benefit from.

hip asked:

Let me ask you a question about the Siglent SDS804X HD, please. When turned on, I observe a constant offset across all channels, but especially on channel one, reaching 1 mV. It takes about 25-30 min for stabilize this offset to 0. The other three channels stabilize a little faster, about 15 minutes. No calibration manipulation or resetting to factory default has any effect. If, after the offset has stabilized, I turn the device off for 5 min and then turn it back on, the offset reappears. Is this a malfunction? If not, why is channel one so different from the others and takes longer to stabilize? I also have a Siglent SDS2104X HD, and its offset when cold is much lower across all channels.
Please see the links for a screenshot of the SDS804 and a photo of the SDS2104. Thank you.

Instrument warm up to full operational temp is a real thing if best accuracy is required.
Most of us are aware that a Self Cal must be done only after some 20-30mins of operation to provide fully reproducible results after the instrument fully warms up.

However we can also activate the Quick Cal feature in the Utility/Maintenance menu to periodically compensate drifts in accuracy while the scope reaches full operating temperature.

Quick Cal momentarily stops measurements while the active channel zero and accuracy is adjusted and those that have used LeCroy DSO's will be familiar with its process.

It could be that hip has performed the Self Cal process with local interference nearby which could impact on the Self Cal result where in his screenshot below there is a 1mV 0V offset on Ch1.
It should be noted, hip mentions his SDS804X HD whereas his screenshot filename tells a different story. 



My SDS814X HD with the same setup AFAICT and with the Quick Cal showing however at time of screenshot it had not run.

[hip]

Hello.
Thank you for posting my question in this helpful thread about this device. I'd be very interested to know what the offset is for other users of this oscilloscope.

I always calibrate after a 30-minute warm-up. If I calibrate cold, the offset goes negative after warm-up.

The fast calibration feature doesn't affect the offset during a cold start, but it maintains it after warm-up. I tried it.

There's no interference near the device; I've tested it in different locations.

Regarding the oscilloscope model, it was originally an SDS804X HD, "upgraded" to an 824. I wondered if the lower-end models use less accurate and stable components.

I'm more interested in why the behavior in one channel is so different from the others and whether this is a malfunction. I haven't noticed this with other Siglent oscilloscopes. That's why I asked.
Thank you.
Best regards, Alex.

[mawyatt]

Alex,

Our SDS800X HD shows very little offset right from startup. Here's a result captured right after power on

Don't worry too much about channel offset and differences, as they are easily resolved with a simple built-in Cal.

WRT component quality, don't think Siglent is skimping anywhere on any DSO models, look at the tear downs and the ADCs used!!

The SDS800X HD is a remarkable instrument for the $ IMO, your selection was a wise choice

Best

[mawyatt]

Here's the results after a good warmup (no self Cal tho). Using the Measurements feature to show the channel offset results as Average, note the Mean of the Average shows the 500 samples Mean of the channel Average.

Best

[hip]

Hi. Thank you very much guys for this info, it was very helpful and  now i clearly see how it should be.
As for the oscilloscope, I really like it. It also has a slightly more responsive interface than my SDS2104X HD.
Best regards,
Alex.

[xKertx]

I’d like to replace the current fan on my SDS802x (upgraded to 200 MHz) with a quieter Noctua fan.
I was thinking that, while I’m at it, I could cut out the restrictive metal grille from the sheet-metal frame entirely and replace it with a wire-style grille like this one, to improve airflow and make it even quieter.
Should I be concerned about EMI shielding? Could removing the metal grille noticeably increase the noise floor or introduce additional interference?

[tautech]

I’d like to replace the current fan on my SDS802x (upgraded to 200 MHz) with a quieter Noctua fan.
I was thinking that, while I’m at it, I could cut out the restrictive metal grille from the sheet-metal frame entirely and replace it with a wire-style grille like this one, to improve airflow and make it even quieter.
Should I be concerned about EMI shielding? Could removing the metal grille noticeably increase the noise floor or introduce additional interference?
(Attachment Link)
(Attachment Link)

FWIW, these are my comments on fan noise a few years back WRT the very similar SDS1104X-E:

regarding: SDS1202X-E is the quietest fan cooled Siglent product other than those that use smart fans (PSU's and SDL E-load) and SDG products are ~ 2x (my guess) the noise level of SDS1202X-E.

OK, all is now shoe boxed alike and needs cooling! Shaking fan's is not the best for crystal oscillators, so we have free PN or jitter added. may will not see much of them, while performance may not that state of the art, this means enough for home workers

Having a Siglent SDG2082x, SSA 3000X Plus & DSO 2000x Plus on the table and one will but some beans in the ear so you can accept those noise. While world went into fan modding as noise less at it get's. Even with a SSD HD, noise level is reduced..

Also, having a Rigol PSU DP832... fan noise with all to gather, loader than inside a car 

Otherwise Tinnitus will your next friend but all likes it cheap, factory to collect each saved penny 

Well you may say that but these instruments require sufficient cooling for stability and long life....a customer needed to quieten his SDS1104X-E and I cut out the grille in my unit.....no change. He fitted a Noctua fan to his unit....no change. We concluded the fans Siglent use are perfectly fit for purpose and the only option to quieten them further was to slow them down....I don't advise this without detailed analysis of the changes to airflow and its effects on instrument thermals and reliability.

[TomKatt]

I won't pretend to fully understand the physics of dynamic fluid flow, but I do know that there is a LOT more going on with fan blade and grille designs than meets the eye.  There is a good chance that opening the center of the grille over the fan hub actually increases noise or results in turbulence that impacts the overall efficiency because most of the air is moved by the edges of the blades and very little at the center.  Siglent could just as easily made the fan grille with more slots - that they did not suggests that the current design is optimal.

With very cheap gear that uses dodgy components there may be improvements through using better parts.  But I think the Siglent gear - while affordable - does not skimp that much where even a top tier fan will be sufficiently better to warrant the replacement.

[xKertx]

I'm not concerned that the noise won't be reduced after the modification. I'm fairly sure that a grille with larger openings and a rounded profile will allow air to flow better and produce less hissing than the sharp stamped holes in the sheet metal.
The holes for connectors are stamped into the sheet metal chassis anyway, so stamping the fan openings doesn't add any extra manufacturing cost. But a separate fan grille, on the other hand, would cost money.
So either these holes are stamped because Siglent is trying to save money, or because the metal chassis serves as EMI shielding and smaller holes allow less electromagnetic interference to enter the device.
And my question was, whether noticeably more electrical interference will get through the larger openings and interfere with the scope's operation. I know from teardown pictures that the analog front-end stages are already enclosed in their own metal shields.

https://www.pugetsystems.com/labs/articles/effects-of-grill-patterns-on-fan-performance-noise-107/

[TomKatt]

So either these holes are small because Siglent is trying to save money, or because the metal chassis serves as EMI shielding and smaller holes allow less electromagnetic interference to enter the device.

I suspect the issue is more about containing any EMI for FCC or similar regulatory requirements than anything to do with shielding the scope from stray EMI regarding noise and accuracy.

[KungFuJosh]

The size of the hole in the sheet metal doesn't save money. I would also assume shielding is more relevant.

[CJSouthern]

I’d like to replace the current fan on my SDS802x (upgraded to 200 MHz) with a quieter Noctua fan.
I was thinking that, while I’m at it, I could cut out the restrictive metal grille from the sheet-metal frame entirely and replace it with a wire-style grille like this one, to improve airflow and make it even quieter.
Should I be concerned about EMI shielding? Could removing the metal grille noticeably increase the noise floor or introduce additional interference?
(Attachment Link)
(Attachment Link)

For what it's worth, I replaced the fan on both my SDS824X HD and SDG3082X (same form factor - and I have one mounted above the other - so I get a double-dose of fan noise) with the popular Noctua. I also installed the less agressive of the two resistors they supply - but made no other changes - and was ... somewhat underwhelmed by the "improvement".

I think it's accurate to say that it's better, but not THAT much better. I can still hear them clearly with my 65 year old ears - they're just a bit less annoying/fatiguing.

I've read the reports of others who have done the more extensive "airflow" modifications including removing the excess metal AND plastic - and I got the impression that theit's was quiter, but I haven't heard it for myself so it's really nothing more than a subjective conclusion.

Thinking through the problem (and, like many, I DO think it's a problem), another possible option would be to disconnect the fan altogether and have air drawn through the device by a larger / quieter fan attached to the rear of an "acoutic shroud" that the scope fits on to (maybe even with some acousic material in bafffles that the air is forced around). Done right I don't think it would add more than a few millimeters to the width and height - and only a minimum extension to the depth.

From what I can tell, a significant amount of the noise seems to either creep around the sides or is reflected from hard surfaces behind it; if you can put some barrier that aligns with the left and right ends - extending backwards - but not obscuring ventilation entry or exit that I suspect that that would help a bit as well.

[TomKatt]

For what it's worth, I replaced the fan on both my SDS824X HD and SDG3082X (same form factor - and I have one mounted above the other - so I get a double-dose of fan noise) with the popular Noctua. I also installed the less agressive of the two resistors they supply - but made no other changes - and was ... somewhat underwhelmed by the "improvement".

I'm inclined to think your 'improvement' is less a result of the 'better' fan and more a result of reduced rpms via the dropping resistor...  Do you know if the cfm's changed as a result?

As for the possible ductwork option, bench real estate is already at a premium for me and while I wouldn't decline a quieter environment, I'm not sure that I would trade bench space and being tied down by ducting to achieve it.

Of course, noise is a funny thing and some people are more sensitive to it than others - if it work for you that's all that matters.

[CJSouthern]

For what it's worth, I replaced the fan on both my SDS824X HD and SDG3082X (same form factor - and I have one mounted above the other - so I get a double-dose of fan noise) with the popular Noctua. I also installed the less agressive of the two resistors they supply - but made no other changes - and was ... somewhat underwhelmed by the "improvement".

I'm inclined to think your 'improvement' is less a result of the 'better' fan and more a result of reduced rpms via the dropping resistor...  Do you know if the cfm's changed as a result?

As for the possible ductwork option, bench real estate is already at a premium for me and while I wouldn't decline a quieter environment, I'm not sure that I would trade bench space and being tied down by ducting to achieve it.

Of course, noise is a funny thing and some people are more sensitive to it than others - if it work for you that's all that matters.

Subjectively, I ran the new fan on 12V straight out of the box and it was noticable quieter; it was only when it was installed that the improvement was less pronounced - thus leading me to suspect that the air being forced through the plastic and the metal grills was probably making it quite turbulent. That's my take on it anyway - it's far removed from my fields of expertise.

Did the CFM change? Again, subjectively, I don't think so. If it did then not by a lot. Interestingly, while I've been developing my control panel for the scope (mostly via a TeamViewer connection to my workbench PC), the scope and sig gen have been on 24/7 for a couple of weeks. A couple of days ago I took the opportunity to assess the temperature of the devices and the exhaust air from the case. There was a touch of warmth above ambience; nothing remarkable. If anything I would describe it as darn near perfect for electronic equipment stability-wise. It's certainly no where remotely close to overheating. If you blew it over your hands after being outside in winter I don't think one would even find it particularly satisfying.

I don't have a lot of bench space spare either - but I don't think a shroud would really impact it much. Just think of some balsa wood and a box that was as wide and as high at the scope that the front 1/2 of the scope slid in to; a "rigid nappy" for the scope's rear if you will. It would by definition increase the depth, but probably not by much more than what's needed for the power cord anyway (assuming one isn't using a right-angle variety); so it probably wouldn't decrease the overall depth that it could be positioned into much if you had a wall behind it. Possibly a good experiment for someone with a 3D printer.

The older I get the grumpier I get with unnecessary noise. Probably an (undiagnosed but suspect) mild autistic trait; if someone bounces a basket ball a few times I'm about ready to shove it down their throat after about the 3rd bounce ...

[KungFuJosh]

The older I get the grumpier I get with unnecessary noise. Probably an (undiagnosed but suspect) mild autistic trait; if someone bounces a basket ball a few times I'm about ready to shove it down their throat after about the 3rd bounce ...

Get a Hioki LCR; it will solve all your other TE's noise issues.

[Martin72]

True, true....

"Older shirts look like new when you put them next to even older ones."

[CJSouthern]

The older I get the grumpier I get with unnecessary noise. Probably an (undiagnosed but suspect) mild autistic trait; if someone bounces a basket ball a few times I'm about ready to shove it down their throat after about the 3rd bounce ...

Get a Hioki LCR; it will solve all your other TE's noise issues.

I used to fly twin-engine piston props for a hobby; do your worst

[xKertx]

I also noticed there's about a 10 mm gap between the outer plastic housing and the inner metal housing, which might also be causing turbulence. It may even trap some of the warm air inside the plastic housing.
I'm thinking of 3D-printing a duct that would be mounted between inner and outer shells and channels all the air directly out.


I was also thinking that if the air flows more easily after installing the duct and enlarging the ventilation openings, the fan won't have to push as hard through small holes, so its speed could be reduced slightly while maintaining the same overall airflow.
But that has to be measured ofcourse.

[CJSouthern]

I also noticed there's about a 10 mm gap between the outer plastic housing and the inner metal housing, which might also be causing turbulence. It may even trap some of the warm air inside the plastic housing.
I'm thinking of 3D-printing a duct that channels all the air directly out.

I was also thinking that if the air flows more easily after installing the duct and enlarging the ventilation openings, the fan won't have to push as hard through small holes, so its speed could be reduced slightly while maintaining the same overall airflow.
But that has to be measured ofcourse.

Possibly the big question is "do people want to make permanent cosmetic changes to their scope that may impact resale value?"

My gut feeling is that if a shroud were fitted that controlled the direction that the noise could travel (leaving everything else the same) then it would probably make a considerable difference. Phase 2 could be to disconnect the internal fan and have air pulled in one side of the shroud and out the other by a bigger/quieter fan attached to the shroud. Both of those option leave the existing plastic and metal in place (which would be my personal preferred option).

Depending on bench layout, one could possibly even just attach a couple of flexible hoses of an appropriate diameter to a shroud and push/pull cooling air from a different place. Personally I think that's probably overkill though.

I'm keen to hear what people come up with though. Maybe even an "accoustic nappy made of cardboard" would be sufficient; easy to try.

[tautech]

Way back in the heyday of the 4ch SDS1000X-E models, fan noise was also a common complaint and the work done back then found the best way to address it was to slow the fan marginally.
Some even went to the trouble to install several thermocouples to monitor temp changes from their mods however the SDS1000X-E didn't in any way have the horsepower of SDS800X HD models....everyone with mechanical knowledge knows to keep the horses cool.

I don't endorse any post factory HW mods as the cooling has been designed to cope with a wide temperature range however in stable and lower temp environments there is no doubt the fan can be slowed a little.

Behind the PW protected Developers Options menu the main device temps are listed however enter this menu at your own risk and please do not share the PW online.

Other Siglent DSO's use much larger and fully temperature controlled fans however these models are in an entirely different price bracket.

[TUMEMBER]

I don't endorse any post factory HW mods as the cooling has been designed to cope with a wide temperature range however in stable and lower temp environments there is no doubt the fan can be slowed a little.

Behind the PW protected Developers Options menu the main device temps are listed however enter this menu at your own risk and please do not share the PW online.

Other Siglent DSO's use much larger and fully temperature controlled fans however these models are in an entirely different price bracket.

Really? And here I thought that an oscilloscope I’ve purchased is my property—meaning that if I wish, I have the right to modify it, "peek" at its software, alter that software, and share the results. Buying a product doesn't equate to signing a corporate clause regarding confidentiality and the transfer of intellectual property rights over one's own research work to the corporation. And by the way, even with the much-maligned Rigol, access to real-time temperature readings isn't hidden away as a paid extra buried deep within the firmware.

[TomKatt]

Really? And here I thought that an oscilloscope I’ve purchased is my property—meaning that if I wish, I have the right to modify it, "peek" at its software, alter that software, and share the results. Buying a product doesn't equate to signing a corporate clause regarding confidentiality and the transfer of intellectual property rights over one's own research work to the corporation. And by the way, even with the much-maligned Rigol, access to real-time temperature readings isn't hidden away as a paid extra buried deep within the firmware.

You can do with your gear - that you paid for - as you like.  I think the only request here is not to publicly share the Developer Menu PW...  There are several settings in that menu that can either cause the oscilloscope to operate incorrectly or even potentially brick it outright.  With the exception of the temp sensors, there is little else of real value for the average user.  While Siglent has turned a blind eye towards the 'upgrade' process, I suspect they may take a different view if suddenly their support dept was overwhelmed by requests for assistance due to users accidently bricking their equipment.  And of course in today's world Siglent gear might suddenly be perceived as problematic, even though the issues were user self inflicted... What were they thinking putting that menu there that kills the machine with just a touch

The PW is out there if you look hard enough.  The request is to kindly not advertise it publicly.  I think that's fair.

PS - when I first got my SDS804X HD scope, curiosity get the better of me and I just had to know what they were hiding behind that menu...  I took a peek and realized the answer is - nothing much to me (except a lot of very scary settings).  I guess the temps were interesting, but really they were all well within safety margins and did not fluctuate much - so I've never gone back in.   You're not missing much.

[KungFuJosh]

The older I get the grumpier I get with unnecessary noise. Probably an (undiagnosed but suspect) mild autistic trait; if someone bounces a basket ball a few times I'm about ready to shove it down their throat after about the 3rd bounce ...

Get a Hioki LCR; it will solve all your other TE's noise issues.

I used to fly twin-engine piston props for a hobby; do your worst

That's appropriate since it's basically a jet engine. 

[BillyO]

Just wait until you get even older.  Natural hearing decline will make your scope quiet. 

[mawyatt]

Just wait until you get even older.  Natural hearing decline will make your scope quiet. 

Yep, even the Hioki IM3536 doesn't bother us too much anymore

Best